finding php json array index number - php

Question

I have a json file with this below format structure.
[
{
"name":"banana",
"type":"fruit",
"rate":10
},
{
"name":"orange",
"type":"fruit",
"rate":20
},
{
"name":"apple",
"type":"fruit",
"rate":30
}
]
I would like to update the rate of the fruit by +1 when i match a search for it.
1 . Read the json file
$json_file = file_get_contents('fruits.txt');
2 . Decoded the json file
$fruit_list=json_decode($json_file,true);
VarDumping the Decoded json file is like this
array (size=3)
0 =>
array (size=3)
'name' => string 'banana' (length=6)
'type' => string 'fruit' (length=5)
'rate' => int 10
1 =>
array (size=3)
'name' => string 'orange' (length=6)
'type' => string 'fruit' (length=5)
'rate' => int 20
2 =>
array (size=3)
'name' => string 'apple' (length=5)
'type' => string 'fruit' (length=5)
'rate' => int 30
Wrote a search function to search the array for fruit name
function search_by_key_and_value($array, $key, $value)
{
$results = array();
if (is_array($array))
{
if (isset($array[$key]) && $array[$key] == $value)
$results[] = $array;
foreach ($array as $subarray)
$results = array_merge($results, search_by_key_and_value($subarray, $key, $value));
}
return $results;
}
$result = search_by_key_and_value($fruit_list,"name",apple);
when the function is supplied with fruit name the whole of json file is searched and the RESULT_MATCH is printed var_dump($result) is like this below
array (size=1)
0 =>
array (size=3)
'name' => string 'apple' (length=5)
'type' => string 'fruit' (length=5)
'rate' => int 30
How can i find the array index number as the result of array index is 0 in the result but its position in the main file point no 3 is indexed at 2 or at-least how can i update the matched retsult rate directly ?